Fluid ejecting mechanism

ABSTRACT

A fluid ejecting mechanism for use in a study device wherein a non-diluted specific minute amount of fluid sample containing particles is ejected by the ejecting mechanism into a flow stream leading to a sensing zone in the particle counter. The ejecting mechanism includes a hollow body having a thermal expansion device mounted therein and a power supply circuit which supplies a predetermined amount of electrical energy to the thermal expansion device to raise the temperature of same a predetermined amount and cause the same to expand thereby to eject from the hollow body a specific amount of fluid sample having a volume displacement equal to the volume increase of the thermal expansion device. Preferably the hollow body is part of a syringe including a plunger. The syringe facilitates the picking up of fluid sample of which only a minute specific portion is ejected toward the sensing zone of the particle counter.

United States Patent 1191 Hogg Jan. 7, 1975 1 FLUID EJECTING MECHANISM705.646 3/1965 Canada 417/383 {75} lnvemorl Walter Hogg, Miami Lakes,,675 3 195 ltaly 4|7/412 [73] Assignee: Coulter Electronics, Inc.,Hialeah,

Fla Primary Lxammer-W1lliam L. Freeh Attorney, Agent, or FirmSilverman &Cass, Ltd. [22] Filed: Aug. 10, 1972 [21] Appl. N0.: 279,436

[57] ABSTRACT [52] U.S. Cl. 417/437, 417/557 [51] Int. Cl. F04b 9/08 Afluld electlng mechamsm for use 11 Study devlce ield Of Search 417/207,322, 412, 383, herein a non-diluted specific minute amount of fluid417/375 379 52 sample containing particles is ejected by the ejectingmechanism into a flow stream leading to a sensing [56] References Cit dzone in the particle counter. The ejecting mechanism UNITED STATESPATENTS includes a hollow body having a thermal expansion de- 9 0 vicemounted therein and a power supply circuit 3 kg; which supplies apredetermined amount of electrical 12/1963 Battista "2'22/3865 energy tothe thermal expansion device to raise the 3 3 7/1964 jf" 4|7/21'2temperature of same a predetermined amount and 3,150,592 8/1962 Stec417/322 Cause the same to expand thereby 1O cicct from the 3,165,6921/1965 lreeli er a] 324/71 hollow body a specific amount of fluid samplehaving 3,270,672 9/1966 Haines 1. 4l7/322 a volume displacement equal tothe volume increase 3,511,583 5/1970 Brown.... 4l7/4l2 of the thermalexpansion device, Preferably the hollow 3.520.641 7/1970 )f----- 417/4l2body is part of a syringe including a plunger. The sy 315981506 8/1971 9417/383 ringe facilitates the picking up of fluid sample of as???" whichonly a minute specific portion is ejected toward 3683212 8/1972 Zoltanjii: .I I... 417/3i2 the sensing 20mg of the Particle counter- FOREIGNPATENTS OR APPLICATIONS Claims, 10 Drawing Figures 1,300,197 6/1962France 417/389 rim/2a.!

PATENTEU JAN 7 975 SHEET 10F 3 sum 2 or 5 PATENTEU JAN 7 I975 J J J .I

1 FLUID EJECTING MECHANISM BACKGROUND OF THE INVENTION The inventionrelates to a non-diluting particle counter and more specifically to adevice for ejecting a non-diluted specific minute amount of fluid samplecontaining particles into a flow stream leading to a sensing zone in theparticle counter.

Heretofore, in the field of particle analysis and particle study, suchas the study of red and white blood cells in a blood sample, it has beencommon practice to dilute the blood sample and then to pass a portion ofthe diluted sample through a sensing zone in a particle study device.The blood is diluted because the normal human blood count is fivemillion cells per cubic millimeter and it is only necessary to study oranalyze one hundredth. of that amount, namely, a volume of 0.01 cubicmillimeters.

In studying a blood sample, the blood cells in a given amount of thesample are counted by passing a portion of the diluted blood samplethrough a sensing zone in a particle analyzing device, such as a Coultertype particle analyzing device which operates on the Coulter sensingprinciple disclosed in US. Pat. No. 2,656,508 issued Oct. 20, 1953 toWallace H. Coulter.

According to this principle, when a microscopic particle in suspensionin a fluid electrolyte is passed through an electrical field of smalldimensions approaching those of the particle, there will be a momentarychange in the electric impedance of the electrolyte in the ambit of thefield. This change of impedance diverts some of the excitation energyinto associated electrical circuitry, giving rise to an electricalsignal. Such signal has been accepted as a reasonably accurateindication of the particle volume for most biological and industrialpurposes.

One apparatus of the Coulter type includes first and second vessels eachcontaining a body of fluid electrolyte. The second vessel is smaller andis immersed in the electrolyte in the first vessel. An electrode extendsinto the electrolyte in each vessel and electric current flows betweenthe electrode through an opening in the side wall of the second vessel,the opening consisting in a minute aperture commonly referred to as aCoulter aperture. Flow of liquid between the vessels is caused byapplying vacuum to the second vessel. According to the Coulterprinciple, particles passing through the aperture from one body ofelectrolyte to the other body of electrolyte will change the impedanceof the electrolyte contained within the aperture and this change inimpedance is sensed by the electrodes. This change generates anelectrical signal in the form of a particle pulse which is then countedby the electrical circuitry of the particle analyzing device.

When making a blood analysis a dilution of blood in electrolyte isplaced in the first vessel. Then vacuum is applied to the second vesselto cause diluted blood to flow from the first vessel through theaperture into the second vessel for a specific period of time. Thesecond vessel is filled with electrolyte, probably including priordilutions.

To make a fairly accurate measurement of particle concentration, onemust accurately measure or meter the amount of fluid which passesthrough the sensing zone during a period of time when the electrical circuitry of the device is operative. This can be accomplished by passingfluid through the sensing zone at a given flow rate for a specifiedperiod of time. Appara' tus utilizing fluid flow metering systems ofthis type in a fluid analyzing device are disclosed in US. Pat. Nos.3,577,162 and 3,654,439.

In most Coulter type particle analyzing devices, the metering isaccomplished with a fluid metering appara tus of the type disclosed inUS. Pat. Nos. 2,869,078, 3,015,775 and 3,271,672. Such meteringapparatus includes a closed fluid system hydraulically connected to thesecond vessel. The closed fluid system includes a connection to a vacuumsource and a mercury manometer. When operating the device, vacuum isapplied to the closed fluid system to raise the mercury in the manometerand to draw some fluid sample into the second vessel. The connection tothe vacuum source is then closed and the manometer, by reason of themercury flowing downwardly to its original position, causes liquid to bedrawn through the aperture and generates signals indicating thebeginning and the end of an analytic run in a period during which anaccurately metered volume of fluid is passed through the aperture. Themetered volume of fluid is equal to the volume within the manometerbetween two electrodes.

It will be understood from the foregoing description ofa Coulter typeparticle analyzing device that it is necessary to dilute a quantity ofblood to make an accurate determination of dilution and to accuratelymeter the fluid flow through the Coulter aperture in order that anaccurate count of blood cells can be made. A simpler way of making theparticle analysis or study would be to pass a specific minute amount ofundiluted blood through the Coulter aperture and thereby eliminate themanometer system. Heretofore this has not been practical since it isdifficult to eject a specific minute amount of undiluted blood into theflow stream of electrolyte flowing toward and through the aperture. Thepresent invention overcomes this difficulty by provid ing a device forejecting a specific minute amount of particle-containing fluid such asblood into the flow stream leading to a sensing zone in a particleanalyzing device. Preferably, the ejecting device is used in a Coulterparticle study device for ejecting a specific minute amount of bloodtoward a coulter aperture thereby providing a non-diluting Coulterparticle counter.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is adiagrammatic view of a particle study device including a verticalsectional view of a sensing zone in the device and a portion ofanejecting mechanism of the present invention positioned adjacent thesensing zone.

FIG. 2 is an enlarged view, partially in section, of the thermalexpansion device of the ejecting mechanism shown in FIG. 1.

FIG. 3 is a schematic diagram of one embodiment of the power supplycircuit of the ejecting mechanism.

FIG. 4 is a schematic diagram of another embodiment of the power supplycircuit of the ejecting mechamsm.

FIG. 5 is a fragmentary side elevational view partially in section ofanother embodiment of the ejecting mechanism of the inventionincorporated into and forming part of a syringe.

FIG. 6 is a vertical sectional view taken along line 66 of FIG. 5 and inthe direction indicated.

FIG. 7 is an enlarged fragmentary sectional view of a modified tip ofthe syringe shown in FIG. 5.

FIG. 8 is an elevational view of a modified syringe, similar to thesyringe shown in FIG. 5, including structure for mountingthe syringe ina predetermined juxtaposed position relative to a vessel in a particlestudy device.

FIG. 9 is a fragmentary side elevational view partially in section of amodified syringe, similar to the syringe shown in FIG. 5, including apiston having a laterally extending passage which facilitates filling ofthe ejecting mechanism.

FIG. 10 is a horizontal sectional view taken along line 10-10 of FIG. 5and in the direction indicated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A particle study devicegenerally of the Coulter type is identified by the reference numeral 10in FIG. 1. The device 10 includes a first vessel 12 having a body offluid 14 therein. A second and smaller vessell6 is situated within thevessel 12 with the lower portion of the vessel 16 immersed in the fluid14. Preferably, and as shown, the vessel 16 is in the form of a tubewhich contains a body of fluid 18. Such a tube is known as an aperturetube and has an aperture in the side wall thereof, the aperture beingformed in a wafer 20 secured to the side wall of the aperture tube 16over an opening in the aperture tube 16. One type of wafer constructionand mounting is disclosed in U.S. Pat. No. 2,985,830.

' As indicated, the upper end of the aperture tube 16 is connected to aconventional vacuum source (not shown) which includes a controlmechanism operable to connect the tube 16 to the vacuum source for apredetermined period of time. The control mechanism also controls theoperation of the circuitry of the particle study device 10, whichcircuitry is generally indicated by reference numeral 22. The circuitry22 includes lead connections to two electrodes 24 and 26 which aresituated, respectively, in the bodies of fluid l4 and 18. An electriccurrent flows between the electrodes through the aperture in the wafer20. When vacuum is applied to the aperture tube 16 a portion of thefluid 14 is drawn through the aperture into the tube 16.

In a conventional Coulter particle study device the body of fluid 14comprises a dilution of blood in an electrolyte such that diluted bloodis drawn through the aperture. Particles such as blood cells in theblood passing through the aperture will change the impedance of theelectrolyte in the aperture. This change in impedance is sensed by thecircuitry 22 which generates an electrical signal, commonly referred toas a'particle pulse, each time a particle passes through the aperture.

The particle pulses produced in this manner are studied, analyzed,and/or counted by the circuitry 22.

In accordance with the teachings of the present invention the body offluid 14 is pure electrolyte and does not contain particles, such aswould be the case in a conventional apparatus. Instead of placing adiluted sample in vessel 12 to comprise the body of fluid 14, theparticle study device 10 of the present invention includes an ejectingmechanism 28 for ejecting fluid sample into a pure body of electrolyte.As will be explained in detail hereinafter the ejecting mechanism 28 isoperable to eject a specific minute amount of undiluted fluid samplesuspension toward the aperture in the wafer 20. In this way the particlestudy device 10 is a non-diluting particle study device.

The ejecting mechanism 28 includes a hollow body 30 having a cavity 32therein. A thermal expansion device 34 is situated in the cavity 32. Asshown, one side wall of the body 30 has an opening 35 thereincommunicating with the cavity 32. The opening 35 is covered by a wafer36 similar to the wafer 20. The wafer has an aperture therein forming anoutlet orifice for the ejecting mechanism 28. This outlet orifice ispreferably very small so that surface tension of the fluid in theorifice will prevent any leakage into or out of the cavity 32 after thecavity 32 has been filled with a quantity of the fluid sample to beanalyzed. The actual size of the aperture forming the outlet orifice isnot critical and it is contemplated that wafers with apertures notmeeting established standards for a Coulter type particle analyzingdevice can be used in the ejecting mechanism of the invention. As aresult, rejected Coulter wafers can be salvaged and utilized in theejecting mechanism of the present invention. A typical wafer will be onehaving an aperture of the order of 50 2 to The thermal expansion device34 is connected via leads 38 and 40 to a power supply circuit 42 of theejecting mechanism 28. The power supply circuit 42 includes acalibratable source of electric energy and circuitry for controlling thedelivery of energy to the thermal expansion device 34 so that only apredetermined amount of electrical energy is supplied to the device 34to produce a predetermined increase in temperature of the device 34 andthereby cause a predetermined incremental increase in the volume of thedevice 34. It will be understood that when the device 34 is heated, itexpands increases in volume. The expansion causes a minute amount of thefluid sample to be ejected through the outlet orifice in the wafer 36.

As best shown in FIG. 2 the thermal expansion device 34 includes a coremember 44 around which is wrapped a resistance element 46, namely a wireconductor, which forms the heating element of the device 34. The core 44and the body 48 form an expandable element generally identified by thereference numeral 49. Surrounding the body 48 is an insulating jacket50. As shown two electrical contacts or terminals 52 and 54 are fixed inthe jacket 50 and connected to the ends of the wire conductor 46. Itwill be understood that the leads 40 and 38 extend to the body 30 andare connected to terminals or contacts fixed in the inner wall of thebody 30 in position to engage the contacts 52 and 54.

The electrical circuit for the power supply 42 can take various forms.One such circuit for the power supply 42 is shown schematically in FIG.3 and is generally identified by the reference numeral 60. The circuit60 includes a voltage source 62 which provides a very accurate, preciseand constant voltage. The voltage source 62 is connected in series witha current limiting resistor 64 and a capacitor 66. The resistor 64controls or limits the charging current to the capacitor 66. Preferably,the resistor 64 has a relatively high resistance so that the chargingcurrent is very low and so that, when the capacitor 66 is connectedacross the resistance element 46, the amount of charging current whichflows through the resistor 64 compared to the current discharging fromthe capacitor 66 is very small. As shown the resistance element 46 isconnected in series with a switch 68 and this series combination isconnected in parallel with the capacitor 66. When it is desired tooperate the ejecting mechanism 28, the switch 68 is closed allowing thecapacitor 66 to discharge through the resistance-heating element 46 andthereby transfer a predetermined amount of energy stored in thecapacitor 66 to the heating element 46. The amount of energy supplied tothe heating element 46 is dependent upon the size of the thermalexpansion device 34, the coefficient(s) of expansion of the expandableelement 49 and the temperature difference needed to obtain a desiredincrease in volume of the expandable element 49. The switch 68 can be aspring biased, push button type switch or can be a relay operatedswitch. In either case the switch 68 is designed not only to dischargethe charge in the capacitor 66 through the resistance ele ment 46 butalso to operate the control mechanism (not shown) for connecting theaperture tube 16 to the source of vacuum. If the switch 68 is of thepush button type, the operator, after depressing the switch 68 willmonitor a conventional visual display device connected to and formingpart of the circuitry 22 and observe the signals produced by particlesin the specific minute amount of fluid sample which pass through theaperture in the wafer 20. When the repetition rate of the signals hasdiminished to a certain point, he will release the switch 68 which willdeactivate the counting circuitry release of the switch could operate aone-shot which applies a signal to the counting circuitry to stopoperation of the same. Alternatively, if a relay controlled switch isutilized, a circuit supplying electric current to the coil of the relaywill be operated by suitable circuitry, such as a flip flop circuit,when the repetition rate of the particle-caused signals diminish belowsome predetermined fraction of the maximum rate, indicating that allejected particles have been counted. In this way the ejecting mechanism28 and the circuit 60 replace and eliminate the prior metering apparatussuch as disclosed in US. Pat. Nos. 2,869,078, 3,015,775 and 3,271,672.

Another electrical circuit for the power supply 42 is shown in FIG. 4and is generally identified by the reference numeral 70. The circuit 70is operable to supply a given quantity of energy at substantiallyconstant voltage and current levels to the resistance element 46. Thisis accomplished by supplying the current from a well regulated voltagesource which maintains a constant, precise, accurate voltage independentof current drain and by integrating the current flowing through theresistance element 46. For this purpose the circuit 70 includes a firstvoltage source 72 which is a well regulated dc. power source andsupplies an accurate, precise, constant voltage. The circuit 70 alsoincludes a switching mechanism comprised of a spring biased start switch74, a normally closed single pole, single throw switch 76 which isoperated by a relay coil 78 and a double pole, single throw switch 80operated by a relay coil 82. An output terminal 84 from the voltagesource 72 is connected to one side of the contacts ofthe switch 74, theother side of the switch 74 being connected to a lead 86 connected tothe switch 76. The other side of the switch 76 is connected by a lead 88to a junction 90. The relay coil 82 is connected between the junction 90and a common conductor 92 connected to output terminal 93 of the powersource 72. The resistance element 46 is also connected between thejunction 90 and the common terminal 92 but in series with a resistor 94which functions as a current sensing resistor. The junction betweenresistance element 46 and resistor 94 is identified by the referencenumeral 95. When the switch 74 is closed a circuit path is establishedfrom the output terminal 84 through the lead 86, the switch contact 76,the lead 88 and the junction 90 to supply electric current to theresistance element 46 and to the relay coil 82.

Energization of the relay coil 82 causes operation of switch 80 toestablish a connection between the output terminal 84 and the lead 86through a lead 96, switch 80 and a lead 98. As a result, switch 74 canbe released and a circuit connection to the resistance element 46 ismaintained via the lead 96, the switch 80, the lead 98, the lead 86,switch 76 and the lead 88.

For the purpose of monitoring or measuring the current flow through theresistance element 46 over a pe riod of time, an integrating circuit isconnected across the current sensing resistor 94 and senses the voltagethereacross, this voltage being indicative of the current through theresistor 94 and hence 46. The inte grating circuit 100 includes anamplifier 102, a capacitor 104 connected between an inverting input 105of the amplifier 102 amd an output 106 of the amplifier 102, and avoltage integrating resistor 107 connected between junction 95 and theinput 105 of the amplifier 102. In effect, the resistor 107 converts thevoltage across resistor 94 to a current which is integrated by theintegrating circuit 100. The resistor 107 is much larger than resistor94 so that only a very small current is integrated. The output from theintegrating circuit 100 is applied to one input 108 of a comparator 100and an accurate, precise, constant voltage is supplied from a secondvoltage source 112 to a second input 114 of the comparator 110. Theoutput 115 of the comparator 110 is connected to one side of the coil78, the other side of the coil 78 being connected to the commonconductor 92.

After a circuit connection has been completed between the outputterminal 84 of the voltage source 72 and the junction 90, current beginsto flow through the resistance element 46 and a very small portion ofthis current is passed through the resistor 107 to the integratingcircuit 100 which accumulates a charge on the capacitor 104. Thischarging of the capacitor I04 re sults in the development of a voltageat the output terminal 106 of the circuit 100 and this developed voltageis applied to the input 108 of the comparator 110 and compared with apredetermined, precise, accurate voltage supplied by voltage source 112to the input 114 of the comparator 110. When the developed voltageequals the supplied voltage, the comparator 110 is operated to energizethe coil 78. Energization of the coil 78 causes opening of the switch 76thereby terminating the current flow through the resistance element 46.In

this way a precise amount of energy, W, is supplied to the resistanceelement 46. The energy W= v f idt. The opening of the circuit connectionto the junction 90 also causes de-energization of the coil 82 which inturn causes the contacts of switch 80 to return to the position shown inFIG. 4. In this position, the switch 80 connects a resistor 116 in shuntrelationship across the capacitor 104 for bleeding any charge on thecapacitor 104 through the resistor 116 thereby to reset the circuit 70,namely the integrating circuit 100, for a subsequent operation thereof.

Again, although not shown in FIG. 4, it is to be understood that theswitch 74 can be of the push button type or of a relay type and isconnected to the circuitry 22 in such a manner that operation of theswitch 74 also initiates operation of the particle analyzing device.Thus, once the switch 74 is closed, the counting circuits of thecircuitry 22 are made operative and the aperture tube 16 is connected tothe source of vacuum for initiating flow of the electrolyte and theejected specific amount of fluid sample through the aperture in thewafer 20. Also, the circuit 70 together with the ejecting mechanism 28eliminates the need for a metering apparatus.

Although two specific circuits, circuits 60 and 70, for the power supply42 have been illustrated in FIGS. 3 and 4 respectively, it is to beunderstood that other types of circuits could be utilized. In thisrespect, instead of utilizing a well regulated power source it ispossible for one to monitor the voltage from a nonregulated voltagesource from which energy is supplied to the resistance element 46 and atthe same time to monitor the current through the resistance element 46.This could be done by connecting a resistor across the voltage sourceand measuring the current therethrough. The current through thisresistor will vary of course as the magnitude of the voltage varies.Then by means of conventional multiplying circuits the current passingthrough this resistor and the current charging the integrating capacitor104 can be multiplied and integrated with respect to time. In this waythe energy input per unit time is integrated and when the energy inputreaches a predetermined value, the circuit connections to the resistanceelement 46 can be opened.

Referring back to FIG. 1, it will be noted that the ejecting mechanism28 is shown schematically and it will be understood that some means mustbe provided for introducing the liquid sample into the cavity 32 withinthe body 30. For this purpose one preferred embodiment of the ejectingmechanism is in the form of asyringe generally identified by thereference numeral 128 in FIG. 5. The syringe 128 includes an elongatebody 129 and a laterally extending projection 130. The projection 130tapers to a tip 131. The projection 130 has a cavity 132 therein inwhich a thermal expansion device 134, similar to the device 34, issituated. An opening in the tip 131 is in communication with the cavity132. The elongate body 129 is closed at one end 136. A plunger 138 isslidably received within the body 129 and extends from an open end ofthe body 129 opposite the closed end 136. The outer end of the plunger138 has a finger manipulatable head 139. The inner end of the plunger138 includes a piston 140 having an L-shaped passageway 142 therein. Thepassageway 142 has one end 143, which opens into space 145 in the hollowbody 129 opposite the closed end 136 thereof, and a second endpassageway 147 which opens onto a side of the plunger 138 and is adaptedto register and communicate with an inner end 148 of the cavity 132during at least a portion of the movement of the plunger 138 within thebody 129.

The thermal expansion device 134 has the same general construction asthe device 34 and has two contacts 152 and 154 thereon for connectingthe heating element therein with the power supply 42. The device 134 canhave any desired cross section, such as a circular cross section,although the preferred cross section is triangular as will be furtherexplained in connection with the description of FIG. 6.

When the plunger 138 is raised, the volume of the space is increased.This increase in volume creates a suction for drawing fluid through theopening in the tip 131 of the projection 130 so long as the end 147 ofthe passageway 142 is in communication with the cavity 132. The fillingof the cavity 132 with fluid sample will continue until the opening 147is completely out of registry with the end 148 of the cavity 132 openinginto the interior of the body 129. At this point the cavity 132 will beclosed except for the opening at the tip 131. When this has beenaccomplished the tip 131 can be placed closely adjacent the wafer 20 andpreferably with the axis of the opening in the tip 131 coaxial with theaxis of the aperture in the wafer 20. The syringe 128 is now ready toeject a specific minute amount of fluid sample toward the aperture inthe wafer 20. This is accomplished by supplying a predetermined amountof energy from the power supply 42 via two leads 158 and 160 to thethermal expansion device 134. The leads 158 and 160 are, of course,connected to contacts which are mounted within the cavity 132 and whichengage the contacts 152 and 154.

To ensure that the plunger 138 is pulled out sufficiently to close theinner end of the cavity 132, a locating projection 162 is mounted on andextends outwardly from the plunger 138. A spring biased latching device164 having a notch 166 which fits over the projection 162 is mounted onthe syringe body 129. When the plunger 138 is raisedthe projection 162will engage and force the latching device 164 outwardly until theprojection 162 is in registry with the notch 166 whereupon the latchingdevice will snap inwardly over the projection 162 andprevent furtherupward movement or downward movement of the plunger 138 due to suctiondeveloped in the space 145. As shown, the latching device 164 has afinger 168 which can be easily manipulated for unlatching the latchingdevice 164 from the projection 162.

As best shown in FIG. 6, the cavity 132 within the projection 130 has acylindrical shape and the thermal expansion device 134 has a generallytriangular cross section such that the device 134 has three longitudinaledges 171, 172 and 173. The contacts 152 and 154 are disposed on theupper edge 171 and the lower edges 172 and 173 engage the cylindricalinner wall surface of the cavity 132. Preferably the thermal expansiondevice 134 has an interference fit in the cavity 132. with the contacts152 and 154 resiliently engaging the mating contacts on the inner wallof the cavity 132. In order to permit an interference fit of the thermalexpansion device 134 in the cavity 132, the insulating jacket thereon isformed from a material having sufficient elasticity whereby the edges172 and 173 can be deformed slightly when the device 134 is inserted incavity 132. Preferably, the insulating jacket material is resilientwhereby the contacts 152 and 154 are urged against the contacts in thecavity 132 to make a good electrical connection therebetween. Thematerial, however, must be incompressable so that deformation thereofdoes not affect the thermal expansion of the thermal expansion device134.

To facilitate easy insertion of the thermal expansion device 134 intothe cavity 132, the cavity 132 is formed in the projection 130 bydrilling a hole transversely through the syringe body 129 and into theprojection 130. This results in a hole 176 on the side of the body 129opposite the projection 130. When the syringe 128 is disassembled forcleaning, the thermal expansion device 134 is then easily removedthrough the hole 176 and, after being cleaned, is reinserted into thecavity 132 through the hole 176.

Also, the L-shaped passageway 142 is easily formed by drilling one holeaxially into the piston 140 and a second hole radially inwardly from theside of the piston 140, the two holes intersecting inside the piston140.

In order to maintain a very small outlet orifice at the tip 131, theopening in the tip 131 is preferably covered by a wafer 178 having avery small aperture therethrough, as shown in FIG. 7.

When the projection 130 is inserted into a fluid sample for filling thecavity 132, some of the fluid sample is picked up by the outer surfaceof the tip 131. To minimize contamination of the electrolyte, the tip131 is preferably wiped off before the syringe 128 is inserted into thebody of electrolyte. However, during the cleaning of the tip 131 with acloth it is likely that fluid in the aperture will be absorbed by thefabric of the cloth. By having a very small aperture volume which ismuch smaller than the specific minute amount of fluid sample to beejected from the syringe 128, this loss of blood from the aperture inthe wafer 178 is insignificant and will not adversely affect theanalysis of the fluid sample. Cleaning of the tip 131, and the possibleabsorption of sample from the aperture by the cleaning wiper, can beavoided by inserting sample into the cavity 132 through the inner end148 thereof, as will be more fully explained in connection with thedescription of FIGS. 9 and 10.

When utilizing the syringe 128 it is desirable to accurately locate andfix the position of the tip 131 relative to an aperture in a wafer in aparticle analyzing or studying device. For this purpose, the syringe 28pref erably has structure associated therewith which cooperates withmating structure on the aperture tube for mounting and holding thesyringe 128 in place. A modified syringe 228 having such mountingstructure is shown in FIG. 8. In this respect the syringe 228 has anL-shaped bar 230 which extends from the syringe with one leg 231 of thebar extending parallel to the longitudinal axis of the syringe. The leg231 of the bar 230 is received in a V mounting block 232 which is fixedto an aperture tube 236. Except for the mounting block 232 the aperturetube 236 is substantially identical to the aperture tube 16 shown inFIG. 1. Also except for the bar 230 the syringe 228 is substantiallyidentical to the syringe 128 shown in FIG. 5. The leg 231 of the bar 230is held firmly in place by a spring 238 fixed to the mounting block 232.

In order to ensure proper location of the outlet orifice of the syringe228, namely, to ensure that it will be coaxial with the aperture in awafer in an aperture tube,

the syringe is preferably fabricated while mounted in a fixture having asimilar shape as the aperture tube 236. A special microscope ispositioned behind an aperture of the fixture, the fixture aperturesimulating the aperture in the wafer, and the outlet orifice in thesyringe 228 is then aligned with the fixture aperture. When the outletorifice is defined by the aperture in wafer 178, the locating of theaperture in the wafer 178 is accomplished by softening the tip 131,which typically is made of glass, and then positioning the wafer inproper location so that the aperture therein is properly aligned withthe aperture of the fixture. Then the glass is allowed to cool andsolidify with the wafer 178 properly in place.

To obviate the need to clean off the tip 131, the syringe 128 can beconstructed in a manner whereby fluid sample is inserted into the cavity132 through the inner end 148 thereof. Such a modified construction ofthe syringe is shown in FIGS. 9 and 10, the modified syringe beingidentified by the reference numeral 328. The syringe 328 is similar tothe syringe 128 and includes an elongate body 329, a projection 330 witha tip 331, a cavity 332, a thermal expansion device 334 mounted in thecavity 332, a closed end 336 and a plunger 338 slidably received in thebody 329.

The plunger 338 has a piston 340 at the inner end thereof received inthe body 329. Instead of an L shaped passageway, such as passageway 142shown in FIG. 5, the piston 340 has a lateral passageway 342 extendingthrough the piston 340. The passageway 342 and cavity 332 are formed inone operation by drilling a hole through the body 329, the piston 340and th projection 330. In this way a hole 346, similar to the hole 176shown in FIG. 5, is formed in the body 329 opposite the projection 330.

To fill the cavity 332 with fluid sample, the piston 340 is manipulatedto bring the passageway 342 into registry with inner end 348 of thecavity 332 as shown in FIG. 9. Then fluid sample, which has been drawninto a hypodermic needle 350 is dispensed into the cavity 332 by holdingthe needle 350 above the hole 346 and manipulating the needle 350 todrop sample, e.g., blood, into the syringe 328 until the level thereofreaches the position indicated by reference numeral 351. Air trappedbelow the fluid sample easily can escape out of the outlet orifice inthe tip 331. The surface tension of the fluid sample, however, preventsfluid flow of the fluid sample through the outlet orifice. After thefluid has reached the level 351, the piston 340 is withdrawn or pushedin until the passageway 342 is completely out of registry with the innerend 348 of the cavity 332. The amount of sample in the passageway 342will, of course be wasted. However, by shearing the body of sample inthe cavity 332 and passageway 342, there is no change in volume of thefluid sample in the cavity 332. As a result the cavity 332 will becompletely filled with fluid sample and is ready for the ejectiontherefrom of the desired specific minute amount of sample.

To prevent contamination of electrolyte the syringe body 329 has itsbottom end 336 closed. The closed space, space 355, between the innerend of piston 340 and the bottom end 336 of the body 329 is vented toatmosphere by means of at least one air channel 359 formed in the outersurface of the plunger 338 as best shown in FIGS. 9 and 10. The ventingof the space 355 prevents a higher or lower pressure from developing inthe space 355, and thereby prevents a pressure differential from actingon the plunger 338. Such a pressure differential makes movement of theplunger 338 unnecessarily difficult and could cause uncontrolledmovement of the plunger 338.

In all other respects the syringe 328 is the same as the syringe 128.Since the syringe 328 does not require wiping off of the tip 331, andsince it can receive blood directly from a hypodermic needle, thesyringe 328 may be preferred in blood analyzing devices over the syringe128.

It will be apparent that the syringes 128, 228 and 328 are simple inconstruction and can be easily assembled and disassembled for cleaningpurposes.

In practicing the teachings of the present invention it is contemplatedthat the core member 44 of the thermal expansion device 34 or 134 willbe formed of either silver or beryllium oxide. Also the material of thebody 48 within which the core 44 is embedded is preferably made fromberyllium oxide. The coefficient of thermal expansion of silver is 10.9and the coefficient of thermal expansion for beryllium oxide is 5.3(10*). As stated above it has been found that a sufficient quantity ofblood for analysis and study of the cells in the blood is 0.01 cubicmillimeters of blood. Assuming a temperature rise of F for the sake ofconvenience and assuming that the expandable element 49 formed by thecore member 44 in the body 48 is cylindrical having a length equal totwice its diameter mathematical calculations show that a silverexpandable element would have to be roughly 0.085 inches in diameter andhave a length of roughly 0.170 inches to obtain an increase in volume ofroughly 0.01 cubic millimeters for a 20F increase in temperature of theexpandable element. This is a very convenient size in that it does notrequire a large syringe. A small syringe can be utilized and a verysmall amount of blood sample is needed. Also the syringe and the thermalexpansion device 34 or 134 are large enough so that they can be readilymade utilizing the techniques used in manufacturing miniature resistors.

If a solid beryllium oxide (BeO) cylindrical expandable element is usedinstead of silver, the volume of the expandable element 49 should beroughly twice the volume ofa silver expandable element. In this case,the diameter of the expandable element would be roughly 0.103 inches andthe length of the element would be roughly 0.217 inches.

Rough calculations show that an expandable element made from BeO wouldrequire 1.09 calories of heat or 4.56 joules of energy in order toobtain an increase of 0.01 cubic millimeters in the volume of theelement, if a temperature rise time of twenty second is assumed, andthat power would have to be expended in the expandable element at theaverage rate of b 0.228 watts.

One of the advantages obtained with a non-diluting particle counterutilizing the ejecting mechanism 28 or the syringe 128 heretoforedescribed is the fact that much more electrolyte is sucked through theaperture in the wafer 20 than blood. The net effect is exactly the sameas if the blood had been diluted. However, dilution does not mattersince all the cells in the 0.01 cubic millimeter of blood ejected intothe body of electrolyte 14 are to be counted.

The electrolyte being drawn through the aperture in the wafer 20 alsoserves as a sheath for the blood cells which flow through the aperture.By ejecting the specific minute amount of blood into the fluid vortexformed adjacent the wafer 20 by the electrolyte being sucked through theaperture, essentially all ofthe blood cells are ensheathed byelectrolyte and drawn through the aperture. As a result practically noneof the blood cells will be lost in the electrolyte.

The duration of sensing and counting of blood cells is not critical in anon-diluting particle study device of the type heretofore described,since the circuitry 22 can be modified to include an electrical circuitwhich will measure the interval between pulses generated by particlespassing through the aperture. When the interval becomes very largeindicating that the expandable element 49 has stopped expanding andblood is no longer being ejected toward the aperture in the wafer 20,the electric circuit 60 or can be operated to terminate the count andterminate operation of the particle study device. in this way,practically all of the blood cells in the 0.01 cubic millimeter arecounted as desired.

Modifications and variations to the ejecting mechanism or the syringeheretofore described will be apparent to those skilled in the art.

What it is desired to be secured by Letters Patent of the United Statesis:

1. Means for ejecting in one stroke a specific minute amount of fluidsample, said ejecting means including means for receiving andtemporarily storing a given amount of fluid sample, said receiving andstoring means having a very small outlet orifice, a solid thermalexpansion device which is mounted within said receiving and storingmeans and which includes an electric heating element, an expandableelement which surrounds said heating element, which is made from amaterial having a given thermal coefficient of expansion and which has agiven volume, and an insulating jacket surrounding said expandableelement and said heating element, and means for supplying apredetermined amount of energy to said thermal expansion device to raisethe temperature of said device to cause said device to expand thereby toeject in one stroke through said outlet orifice a specific minute amountof fluid sample from said receiving and storing means.

2. The ejecting means according to claim 1 wherein said receiving andstoring means is a syringe.

3. The ejecting means according to claim 1 wherein said receiving andstoring means includes a body having a fluid receiving cavity thereinand said outlet orifice being in a wall of said body and communicatingwith said cavity, said solid thermal expansion device being situatedwithin said cavity.

4. The ejecting means according to claim 1 wherein said energy supplymeans includes a voltage source having good regulation to provide asubstantially constant voltage independent of current drain.

5. The ejecting means according to claim 1 wherein said expandableelement is made of silver.

6. The ejecting means according to claim 1 wherein said expandableelement is made of beryllium oxide.

7. The ejecting means according to claim 1 wherein said expandableelement is made of silver and beryllium oxide.

8. The ejecting means according to claim 1 wherein said thermalexpansion device includes an electric heating element and said energysupply means includes a voltage source, an energy storing device forstoring a predetermined amount of energy and switch means for connectingsaid storage means to said heating element to discharge saidpredetermined amount of energy from said storage device into saidelectric heating element.

9. The ejecting means according to claim 1 including means for mountingsaid ejecting means in position for ejecting the specific minute amountof fluid sample toward a sensing zone in a particle study device.

10. The ejecting means according to claim 1 wherein said heating elementis a wire conductor and said expandable element includes an elongatedcore on which said wire conductor is wound, said heating element andsaid core being embedded in a body which forms part of the expandableelement.

11. The ejecting means according to claim wherein said core and saidbody are made of the same material.

12. The ejecting means according to claim 1 wherein said thermalexpansion device includes an electric heating element and said energysupply means includes a voltage source, switch means for connecting saidvoltage source to said heating element and circuit means connected tosaid switch means and said heating element for monitoring the energyinput to said heating element and for opening the connection betweensaid voltage source and said heating element after a predeterminedamount of energy has been supplied to said heating element.

13. The ejecting means according to claim 12 wherein said circuit meansincludes means for integrating the current flowing through said heatingelement, a second voltage source, a relay including an operating coiland contacts in the connection between said first voltage source andsaid heating element, and a comparator having inputs connected to saidintegrating means and said second voltage source and an output connectedto said operating coil, said comparator being operable to compare avoltage developed in said integrating means with a constant voltagesupplied from said second voltage source and to energize said coil forcausing opening of said contacts when said developed voltage equals saidconstant voltage.

14. The ejecting means according to claim 1 wherein said receiving andstoring means includes an elongate hollow body, a projection whichextends from said body, which is integral with said body, which has acavity therein communicating with the hollow interior of said body, andwhich has a tip at the distal end thereof, said tip having said outletorifice therein communicat ing with said cavity, and a plunger in saidbody, said plunger having a passageway therein, said passageway having afirst end which opens into said hollow body opposite a closed end ofsaid hollow body and a second end which opens onto a side of saidplunger and which is adapted to register and communicate with saidcavity during at least a portion of the movement of said plunger withinsaid body, and said thermal expansion device being situated in saidcavity.

15. The ejecting means according to claim 14 wherein said body is openat one end opposite said closed end and said plunger has a portionthereof which extends outwardly from said open end of said body, andwherein said receiving and storage means includes means for limitingoutward movement of said plunger to a position where said second end ofsaid passageway is completely out of registry with said cavity.

16. The ejecting means according to claim 14 including means formounting said body in a particle study device with said tip in apredetermined position relative to a sensing zone in said particle studydevice.

17. The ejecting means according to claim 1 wherein said receiving andstoring means includes an elongate hollow body and a projection whichextends from said body, which is integral with said body, which has acav ity therein communicating with the hollow interior of said body, andwhich has a tip at the distal end thereof, said tip having said outletorifice therein communicating with said cavity, and said body having ahole therein opposite said projection and wherein a plunger is receivedin said body through an open end thereof and has a lateral passagewaytherethrough which is adapted to be brought into registry with the innerend of said cavity for enabling filling of said cavity with fluid samplethrough said hole and said passageway.

18. The ejecting means according to claim 17 wherein the end of saidbody, opposite said open end thereof is closed, and said plunger has atleast one channel therein communicating the space between said closedend of said body and the inner end of said UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION PATENT NO. 3,859,012 DATED August 18, l975INVENTOR(S) WALTER R. HOGG It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 2, line 46, change "coulter" to Coulter Column 6, line 36, change"amd to and Column 10, line 32, change "th" to the twenty-eight D 3) ofOctober 1 975 [SEAL] A ttes t:

RUTH C. MASON Arresting 0mm C. MARSHALL DANN Commissioner of Patents andTrademarks

1. Means for ejecting in one stroke a specific minute amount of fluidsample, said ejecting means including means for receiving andtemporarily storing a given amount of fluid sample, said receiving andstoring means having a very small outlet orifice, a solid thermalexpansion device which is mounted within said receiving and storingmeans and which includes an electric heating element, an expandableelement which surrounds said heating element, which is made from amaterial having a given thermal coefficient of expansion and which has agiven volume, and an insulating jacket surrounding said expandableelement and said heating element, and means for supplying apredetermined amount of energy to said thermal expansion device to raisethe temperature of said device to cause said device to expand thereby toeject in one stroke through said outlet orifice a specific minute amountof fluid sample from said receiving and storing means.
 2. The ejectingmeans according to claim 1 wherein said receiving and storing means is asyringe.
 3. The ejecting means according to claim 1 wherein saidreceiving and storing means includes a body having a fluid receivingcavity therein and said outlet orifice being in a wall of said body andcommunicating with said cavity, said solid thermal expansion devicebeing situated within said cavity.
 4. The ejecting means according toclaim 1 wherein said energy supply means includes a voltage sourcehaving good regulation to provide a substantially constant voltageindependent of current drain.
 5. The ejecting means according to claim 1wherein said expandable element is made of silver.
 6. The ejecting meansaccording to claim 1 wherein said expandable element is made ofberyllium oxide.
 7. The ejecting means according to claim 1 wherein saidexpandable element is made of silver and beryllium oxide.
 8. Theejecting means according to claim 1 wherein said thermal expansiondevice includes an electric heating element and said energy supply meansincludes a voltage source, an energy storing device for storing apredetermined amount of energy and switch means for connecting saidstorage means to said heating element to discharge said predeterminedamount of energy from said storage device into said electric heatingelement.
 9. The ejecting means according to claim 1 including means formounting said ejecting means in position for ejecting the specificminute amount of fluid sample toward a sensing zone in a particle sTudydevice.
 10. The ejecting means according to claim 1 wherein said heatingelement is a wire conductor and said expandable element includes anelongated core on which said wire conductor is wound, said heatingelement and said core being embedded in a body which forms part of theexpandable element.
 11. The ejecting means according to claim 10 whereinsaid core and said body are made of the same material.
 12. The ejectingmeans according to claim 1 wherein said thermal expansion deviceincludes an electric heating element and said energy supply meansincludes a voltage source, switch means for connecting said voltagesource to said heating element and circuit means connected to saidswitch means and said heating element for monitoring the energy input tosaid heating element and for opening the connection between said voltagesource and said heating element after a predetermined amount of energyhas been supplied to said heating element.
 13. The ejecting meansaccording to claim 12 wherein said circuit means includes means forintegrating the current flowing through said heating element, a secondvoltage source, a relay including an operating coil and contacts in theconnection between said first voltage source and said heating element,and a comparator having inputs connected to said integrating means andsaid second voltage source and an output connected to said operatingcoil, said comparator being operable to compare a voltage developed insaid integrating means with a constant voltage supplied from said secondvoltage source and to energize said coil for causing opening of saidcontacts when said developed voltage equals said constant voltage. 14.The ejecting means according to claim 1 wherein said receiving andstoring means includes an elongate hollow body, a projection whichextends from said body, which is integral with said body, which has acavity therein communicating with the hollow interior of said body, andwhich has a tip at the distal end thereof, said tip having said outletorifice therein communicating with said cavity, and a plunger in saidbody, said plunger having a passageway therein, said passageway having afirst end which opens into said hollow body opposite a closed end ofsaid hollow body and a second end which opens onto a side of saidplunger and which is adapted to register and communicate with saidcavity during at least a portion of the movement of said plunger withinsaid body, and said thermal expansion device being situated in saidcavity.
 15. The ejecting means according to claim 14 wherein said bodyis open at one end opposite said closed end and said plunger has aportion thereof which extends outwardly from said open end of said body,and wherein said receiving and storage means includes means for limitingoutward movement of said plunger to a position where said second end ofsaid passageway is completely out of registry with said cavity.
 16. Theejecting means according to claim 14 including means for mounting saidbody in a particle study device with said tip in a predeterminedposition relative to a sensing zone in said particle study device. 17.The ejecting means according to claim 1 wherein said receiving andstoring means includes an elongate hollow body and a projection whichextends from said body, which is integral with said body, which has acavity therein communicating with the hollow interior of said body, andwhich has a tip at the distal end thereof, said tip having said outletorifice therein communicating with said cavity, and said body having ahole therein opposite said projection and wherein a plunger is receivedin said body through an open end thereof and has a lateral passagewaytherethrough which is adapted to be brought into registry with the innerend of said cavity for enabling filling of said cavity with fluid samplethrough said hole and said passageway.
 18. The ejecting means accordingto claim 17 wherein the end of said body, opposite said open end thereofis Closed, and said plunger has at least one channel thereincommunicating the space between said closed end of said body and theinner end of said plunger to atmosphere.